Signaling system



8, 1936- A. A. LlNsr-:LL 2,063,610

SIGNALING SYSTEM Filed July 27, 1953 4 Sheets-Sheet 1 I.. .L RN Y wu WMNAZ/R wn .m NE v im A l. A

. 8, 1936. A. A. LlNsELL.

SIGNALING SYSTEM 1 4 Sheets-Sheet 2 Filed July 27, 1933 L'gfcz ale/vfINVENTOR ALFRED A. LINSELL KQ ATTORNEY Dec. 8, 1936. A. A. I INSELL.

SIGNALING SYSTEM Filed July 27, 19:53

Zi/'5.5. @W4 7 6@ Elvia 4 Sheets-Sheet 3 Off/maf fifi;Ju

@tips Si 6 INVENTOR ALFRED A. LINSELL BY M ATTORNEY Den.` 8, 1936. VA, A|NSEL L 2,063,610

SIGNALING SYSTEM Filed July 27, 1935 4 Sheets-Sheet 4 JiaN 70 INVENTORALFRED A UNSELL ATTORNEY Patented Dec. s, v192.6`

SIGNALING SYSTEM AlfredfAubyn Linsell, London, England, assignor to`Radio Corporation of America, a corporation of Delaware Application July27, 1933, Serial No. 682,415

In Great, Britain July 28,1932

9Claims.

This invention relates to radio signaling systems, and has for itsobject to provide an improved signaling system vwherein a visual indica--tion is given at the receiver of information which it is desired toconvey, said visual indication being such that it may be easily andrapidly read, and does not necessitate the knowledge of any code, suchas a Morse code, on the part of an observer for whom the information isintended.

Although by no means limited thereto one of the principalapplications ofthe invention is to direction finding or direction indicating systemswhether of the radio beacon type, by which expression is meant atransmitter emitting a directional beam which is rotated about thetransmitter, or of the type wherein a signal is broadcast by atransmitter the bearing of said transmitter with respect tota receiverbeing in this case determined by a directional receiver.

The invention may however be employed for the conveying of any desiredinformation and a further important application is concerned with thetransmission by wireless to aircraft and the like ofinformation relatingto such matters as weather conditions, and in carrying out the inventiona "picture or visual indication of the message transmitted which maycomprise a plurality of items of information is received but without thecomplications and synchronizing diculties of a television or facsimiletelegraph` system.

According to one feature of the invention there is provided at thetransmitter means for generating a plurality of different modulating, e.g. note,

'frequencies and means for separately adjusting 1 the amplitudes thereofbetween zero and a predetermined maximum, and the adjusted modulatingfrequency amplitudes are utilized to modulate a transmitted carrierwave, the relative proportions of the 'modulating note frequenciesdetermining the` information it is desired to convey.

The receiver'` is provided with means responsive to the relativeamplitudes of the modulating frequencies for controlling indicatingmeans in dependence uponv the said relative strengths of saidfrequencies. i

According to a further feature of the invention, the indicating meansemployed at the receiver comprises a cathode ray tube and means forapplyingcontrol potentials thereto in dependence upon the strength ofthe received modulating frequencies for controlling the direction of thecathode ray. The cathode ray tube may be provided with a single targetinthe form of a fluorescent screen marked in any desired manner, the

(ci 25o-11) A Figure 2 illustrates the essential features of a receiverby means of which waves sent out by the transmitter of Figure `1 may bereceived.

Figures 3 to 5 inclusive illustrate modificationsV of the cathode raytube included in the receiver of Figure 2. l

Figures 6 and 7 illustrate modifications of the fluorescent screen ortarget of the prior cathode ray tubes; while,

Figures 1a and 1b illustrate a modification of the transmitter of Figure1.

In accordance with the Vfirst embodiment to be described a radio beaconsystem of direction indi- /cation comprises at the transmitter means formodulating a continuously rotated beam of radiated carrier energy by adifferent combination of a plurality of note frequencies for eachinstantaneous position of the beam. In the particular arrangement nowunder consideration only four modulating frequencies are required andthe carrier wave is modulated at any instant with a combination of twoof said frequencies in predetermined power ratios depending upon the`instantaneous position of the beam. For example, when the beam is in thequadrant between the compass points north and east the transmitter ismodulated by a combination of two note frequencies of 500 and 600 cyclesrespectively the power ratio of 600 cycle modulation to 500 cyclemodulation being equal to the tangent of the angle through which thebeam, assuming clockwise rotation, has rotated from north. When the beamis pointing due north the value of the 600 cycle modulation will be zeroand the value of 500 cycle modulation a maximum. Similarlywhen the beamis pointing due east the value of the 500 cycle modulation will be zeroand that of the 600 cycle modulation a. maximum. For the second quadrantbetween the cardinal points east and south the transmitter is modulatedin a similar manner by a combination of, say, 600 and 700 cycles, for

the third quadrant'between South and West by av combination of, say, 700`and 800 and for the fourth quadrant between West and .Northby acombination of 8 00 and500 cycles. l

An arrangement whereby the transmitter may be modulated asV above Ydescribed is illustrated schematicallyv 'in Vthe accompanying lFlgnre lwherein G1, Gi, Ga, G4 are four notefrequency ,generators providingmodulating frequencies of\ 500,'600, 700, and 800 cycles respectively..Potentiometers Pi, P2. Pa, P4 are connected across lsaid generators andin seriesV with one lanother as ciated and that the directiony ofdeflection of the cathode ray will therefore be dependent upon therelative strengths Aof the incoming audio frequencies'. v i

Assumingfor the moment that the radiated energy were .received atconstant strength throughout the complete cycle of rotation of the beam,the cathode ray at the receiver would be deflected to produce a luminousspot upon the fluorescent-'screen which spot will travel round acirclein synchronism with the rotation of the shown between the grid andcathode of a valve` V connected for choke modulation o'f a transmitter Tcoupled at M to a suitable rotating beam aerial (not shown). Drepresentsthe highy frequency.

energizing source for the transmitter T. `|Ilie sliding contacts ofthe'potentiometers may be actuated automatically under the control ofthe rotating beam aerial for obtaining the required combination of audiofrequencies in the yappropriate ratios corresponding position of thebeam.

to the instantaneous beam'. In view, however, of the fact that thereceived signal strength will be a maximum at thel instant the beampasses through the receivling station and will rapidly fall offsubstantially -to zero during the greater part of the cycle of rotationand will rise again to a maximum as the i beam again passes through thereceiving station,

4At the receiverthe signals are-amplied and detectedin anyconvenientmanner well known per se and are utilized to give a'direct visualindication of the'bearing of the receiver withrespect4 to thetransmitter. A suitable form of rejmay also. be employed, though withdifferent markings, to enable an aircraft not carrying a ceivingapparatus for achieving this result is illustrated schematically in theaccompanying Fig'- ure 2, a modified indicating arrangement `being shownin Figure 3.

" Referring t Figure 2. a non-directional receiv-v 'ing aerialA is showncoupled toa high frequency amplifier HFA in t'urn coupled to adetectorvalve DV in whose anode circuitare connectedy in series with one anotherthe primaries ofV four transform-` ers T1,TI'2, 'I3,T4 whose primary andsecondary windingsareI coupled by means of vibrating reeds or tuningforks whose natural frequencies are 500, 600, 700, and 800 cyclesrespectively. These transformers thus constitute selector circuits forthe four modulating frequencies and the/secondary windings of the saidtransformers Aare connected as shown through rectiflers R1, R2, acrossresistancesri, n, r3, r4. Any meansfor indicating the energy dissipatedin the -resistances r1, r2, r3, r4 may be used.v Preferably the negativeend of eachof the resistances may be connected as shown in Figure 2 to acommon point P while the positive ends thereof are connected as showntov four electrostatic deiiecting plates N, E, S, W of a cathode rayoscillograph tube C. The common point P is connected to the cathodepoint of the tube C. One suitableform of cathode ray tubeis illustrateddiagrammatically in Figure 2 and comprises the vusual cathode andaccelerating elements of;,an electron gun, two pairsI of electrostatic.deflecting electrodes 'NS, EW for controlling the` cathode ray and afluorescent,l

screen FS `formed inthe end of the tube and marked with the points ofthe compass. lThe deflector electrode N associated with the 500 cyclefrequency selective circuit T1, R1, R'.is positioned to attract or deectthecathoderaytowards that part of the fluorescent screen ymarked North,the electrode E associated with the 600 cycle frequency selectivecircuit Ta, Rara towards that part markedfEast and so forth tocorrespond tothe directions assigned to the different frequencies at thetransmitter.

Morse code operator. to ascertain the identity of a beacon station ofthe non-directional vtype whose bearing has been found by the .usualdirection ilndingmethod. To this end the invention envisagescharacterizing beacon stations by modulating the carrier wave of each ofa plurality of beacon stations of the broadcast or'non-directional type'withv a combination of two `audio frequencies in a fixed predeterminedratio. As before, four frequencies can be used and any two combined indifferent degrees of powerto identicordancewith the modulationfrequencies of the appropriate station.

An alternative form of cathode ray tube to that shown in Figure 2 isshown diagrammatically` in Figure 3 wherein in place of a uorescentscreen a plurality of radially disposed target Relectrodes t is employedeach appropriate to a particular transmitting station. A suitable relay,not shown, is connected in circuit with veach target [whereby said-relayis actuated by the cathode ray impinging upon the associated target inaccordance with received signals as already described. The relay maytake the form of a neon lamp givingva direct visual indication or may beutilized to actuate any desired form of indicator..

An alternative form of indicating cathode ray device which renders theuse of separate vfrcquency selective circuits unnecessary is showndiagrammatically in the accompanying Figure 4 and comprises a cathoderay tube C into the .usually provided, re-entrant tubular stem s ofwhichis inserted one end of an electromagnet em whose l It will be obviousthat the potential drop across any resistance will be proportional tothe strength f of the particular audio frequency occurring in theselector circuit with which` the resistance is'assowindingw is feddirectly with the demodulated received signals. Mounted on the pinch ofthe cathode 'ray tube are the usual elements of, V

an electron gun and surrounding the latter is a plurality of tuned reedsof magnetic material arranged parallel to the axis of the tube. In

the particular arrangement illustrated four of these reeds are providedtuned to 500, 600, 700,

and 800 cyclesand positioned 90 apart about a`v circle whose center ison the axis of the tube. A suitably marked fluorescent screen FS isprovided at the end of the tube and for convenience this may be markedwith a plurality of cons centric circleseach having a scale of degrees,the

ray.

Provided that all of the reeds are at rest the net deflection producedon the cathode ray will be nil; but if one or moreV of the reeds vibratein response to an incoming signal the cathode ray will be vibratedtowards such reed or reeds. Thus if the incoming signals afterdemodulation contain at a given instant frequencies of 500 and 600cycles at relative strengths of say 3:1 the reeds tuned to thesefrequencies would be set into vibration by the electromagnet em the 500cycle reed vibrating at substantially three times the amplitude ofvibration of the 600 cycle reed and the ray would therefore be deflectedalong a path previously `described arrangement.

In a modification of the last described system, wherein non-directionalbeacon stations are each modulated with a characteristic modulatingfrequency combination, each station transmits a carrier modulated with asingle note frequency. e. g. 50, 60, '10,or 80 cycles, and so forth. theoutput from the detector at the receiver being fed to the coil w of anelectromagnet em symmetrically disposed with relation to a plurality ofcorresponding tuned reeds, each reed having a natural frequencycorresponding to the modulating frequency characteristic of one of thestations in question. The reeds may be associated with a suitable dialmarked opposite each reed with the name of the appropriate station togive a direct visual indication of the station being received or theymay be utilized to control `the deflection of the cathode ray of acathode ray tube as above described with the exception that in this casea separate tuned reed corresponding to each stations or with a pluralityof targets and associated relays as before.

The application of the invention to the transmission of infomationrelating to weather conditions is illustrated in the accompanying Figure6 which shows the method of marking the fluorescent screen of theindicating cathode ray tube at the receiver.

given.

It is assumedr in connection with this application that it is desired totransmit to an aircraft the following five items of informationsimultaneously: Y t

(1) The direction of the wind.

(2) The force of the wind.

(3) Visibility.

(4) Base of cloud.

(5) Temperature.

Referring to Figure 6 it'willqbe seen that one quadrant is marked with abase of cloud scale having radial divisions numbered, say, 0-100 meters.A second quadrant is marked with a temperature scale having radialdivisions numbered, say, 30-100 F. A third quadrant is marked with astrength of wind" scale having radial divisions numbered, say, 0-80miles per hour. while the fourth quadrant is marked with a visibilityscale having radial divisions numbered, say, 0-10 kilometers'. Arrangedabout the periphery of the end wall of the tube and surrounding theabove scales is a fthscale marked with the cardinal poi'nts of thecompass N. E. S. W. and having divisions numbered 0-3 60 for indicatingthe'direction of the wind.

By means to be described later, the cathode ray is deiiected to cause aluminous spot to appear in each quadrant of the iiuorescent screen toindicate the appropriate scale division. Indication of the appropriatedivision on the outer circular scale is effected by oscillating thecathode ray to produce a radial line of light opposite Figure '1 issimilar to Fig- Y ure 6 and shows the type of indication which is saiddivision. In this way an indication appropriate to the outer scale isdistinguished from those appropriate to the inner scales in fourquadrants. In practice the ve indications are repeated one after theother in rapid succession,

so that as a result of persistence of vision.' the indications appear tothe eye to be effected simultaneously and continuously.

Figure 7 shows the manner in which various indications appear on thefluorescent screen, X being the indication appropriate to the outerscale of wind direction, Y the luminous spot indicating the strength ofwind and Z the luminous spot indicating visibility. Base of cloud andtemperature are indicated a similar manner to strength of wind andsibility, but the former scales have been omitted from Figure '7 for thesake of clarity.

The required information is sent out from a radio transmitter whereofthe high frequency carrier is modulated with a combination of two notefrequencies in predetermined power ratios for each item of infomation.As in the rst described arrangement, only four modulating frequenciesare required from'which the required pair of frequencies is selected.These audio frequencies are separated out at the receiver and yappliedto the cathode ray tube in such manner that the ray is deflected on thefluorescent screen to the appropriate mark concerned.

Considering first the indication relating to the direction of the wind:If the `wind is due north, the transmitter is modulated with a frequencyof, say, 500 cycles. If the wind is due east, the transmitter ismodulated with a frequency of, say, 600 cycles; if due south, say, 700cycles; and if due west, say, 800 cycles. For any direction betweennorth and east the transmitter is moducycle modulation to 500 cyclemodulation being lequal to the tangent ci the angle between themodulated with-two frequencies of 500 and 600 i cycles per second',the-latter being of zero amplitude, while for due east the formerfrequency is of 'zero amplitude, Similarly for directions between keastandsouth, the transmitter will vbe modulated iwitn a combination of 600cycle and '700 cycle modulation frequencies, and so on for theremainingquadrants. The oscillation of the cathode ray to produce aradial line of light on the uorescent screen, whereby the transmitteddirection is indicated, is eected, in amanner to be described later, byvarying the total amount ci high frequency energy radiated from thetransmitter, thereby causing the cathode ray to travel back xand forthalong the said line at a speed such as to make the radially moving spotappear as a` line. l

The other items of information are transmitted in regular succession ina similar manner, the

temperature, say, beingl indicated by a combination in appropriate ratioof 500 and 600 cycles.

` For extreme values one frequency maybe of zero amplitude. Thestrengthof wind may be indicated by an appropriate combination of 600 and 700cycles, they visibility by a suitable combination of 700 and 800 cycles,and the base of cloud by acombination of 800 and 500 cycles.

t The apparatus at the transmitter is substanti'ally the same as in thefirst arrangement herein described and illustrated in Figure 1 with theexception that the said transmitter is a non-directional or broadcasttransmitter and not a radio beam-radiating a rotating directional beam.The 'transmitter may comprise as shown in Figure 1a a plurality ofsources of tone frequencies I and 5, 2 and 6, 3 and l, 4 and B,connected asshown by variable coupling means Pi, Pa, Pa, P4' tothecontrol grid-"of-.a thermionic relay 9, the anode electrodeof whichdraws its currenty from a source which also` supplied current to theanode circuit of an oscillation generator I oi' the regenerative type.The oscillations producedlin I0 and moddirection to be indicated andnorth. Thus, for due north, the transmitter may be regarded as thatshown in Figure 2 with the exception that the fluorescent screen ismarked as. indicated in Figures 6 and "I.

Having now particularly described and ascertained the nature of my saidinvention and in' what manner the same is to be clare that what I claimis:

1. A` radio beacon system comprising means for radiating a continuouslyrotating beam of vcarrler waveenergy, means for simultaneouslygenerating a plurality of 'different modulating frequenciesrmeans formodulating the radiated carrier` wave energy by a combination of two ofsaid modulatingfrequencies, in a strength ratio `de pendent upon theinstantaneous position of the beam and receiving means including acathode ray tube havinga fluorescent screen and horizontal and verticaldeecting circuits operative in dependence upon the relative strengths ofsaid modulating frequencies for producing an indication upon saidscreen.

2. A radio beacon system as claimed in claim 2 and in which the carrierwave energy is modulated by the combination of a pair of frequenciesappropriate to Iand characteristic of each quadrant through which thebeam passes the two freperformed, I dequencies of each pair beingcombined at any inulated by the desired tone frequencies in the d'e-kthe required combination of audio `frequencies.l in the appropriateratios corresponding to the direction of the wind- The `potentiometersliders Si, S2 etc. may also be operated as shown in Figure 1b by amotor MI .acting .through camsl I to I1 inclusive. The cams may beshaped and stant in a strength ratio which varies as said beam movesthrough said quadrant so that said strength ratio is characteristic ofthe instantanecusposition of said beam in said quadrant.

3. Transmitting means comprising a plurality of sources ofmodulatingpotentials of different frequencies, a thermionic relay tube having ananode, control grid and cathode, variable coupling means between each ofsaid sources and the control grid -and cathode of said relay tube,selected pairs of said coupling means being variable in 'oppositesenses, transmitting means including a source of local oscillations onwhich said modulating potentials are impressed coupled with the anodeand vcathode of said tube, directional radiating means coupled. to saidtransmitting means, and means 'for 'rotating .said radiating Ameans yandsimultaneously-varying said coupling means.

4. Signaling meansincluding four sources of modulating potentials offrequencies which diner byv alike amount, a therniionic relay tubehaving an anode,a cathode and a control grid, a variable impedancecoupling each of said sources to the :control grid and cathode of saidtube, the

staggered to produce thedesired result; Inlike manner, where convenient,the control `'of the appropriete potentiometer may be effectedautomatically for the other items of information, e. g. by

vathermometer for temperature indication.` The .power radiated 4may beiiuctuated for the purpose of oscillating the cathode ray atthe receiverto produce a line indication for the direction ofwind reading-in anyconvenient way, for example, by varying the coupling M of Figure 1abetweeny the transmitter and the transmitting vantenna, `or byapplying-an alternating potential to the grid of one of thetransmitterpower am- The apparatus at the receiver .is the same as ilrst andsecond, second and third,-third and `fourth, and fourth and first ofsaid impedances being variable in opposite sense, transmitting meansincluding a source of local oscillations connected to the anode andcathode of said tube,

directional radiating means coupled to said transmitting means, andmeans for rotating said radiating means and' simultaneously controllingsaid impedances.

A5. Transmitting means comprising a plurality of sources of modulatingpotentials, a potentiometer connected'in parallel with each source, a

thermionic relay' tube, a' connection between the control grid of saidtube and a point on the rst of said potentiometers, a connection betweena point on a second potentiometer and the terminal ot said firstpotentiometen, a connection between the terminal of said secondpotentiometer and a moving point on a third potentiometer, a convnectionbetween the terminal of the th`ird potentiometer and a moving point on'a fourth `ing means, a plurality of mechanical devices each tuned to adiiferent modulatingI frequency, each device comprising an input windingand an output winding and a frequency stabilizing element associatedwith said windings, a circuit connecting said input windings in seriesbetween the output electrodes of said tube a rectifier in series witheach of said output windings, a cathode ray tube, a connection betweenone terminal of each of said rectiers and the cathode of `said cathoderay tube, said cathode ray tube having a plurality of pairs ofdeiiecting plates and a connection between the free terminal of each ofsaid rectiers and one of said deflecting plates. K

7. In a signaling system', signal absorbing means, signal amplifyingmeans coupled to said absorbing means, a thermionic demodulator tubehaving an input circuit coupled to said signal amplifying means, avplurality of mechanical vibratory devices each tuned to a differentmodulating frequency, each device comprising an input winding and anoutput winding, a circuit connecting said input windings in seriesbetween the output electrodes of said tube, a rectifier and a resistanceconnected in series with each of saidoutput windings, a cathode raytube, a connection between one terminal of each of said resistances andthe cathode of said cathode ray tube, said cathode ray tube havingacplurality of pairs of deilecting plates and a connection between thefree terminal of each of said resistances and one of said deflectingplates.

8. Transmitting means comprising a plurality of sources of alternatingcurrent of tone frequency, said frequencies increasing progressivelyfrom the first source to the last source, a potentiometer connected inparallel with each of said sources, a thermionic tube having anode,

Vcathode and control grid, a connection between the movable point oneach said potentiometer and the control grid of said tube, means forconnecting in series the several potentiometer portions which liebetween the movable points and thel corresponding terminals of eachpotentiometer, the terminal of the last potentiometer being 'connectedto the cathode of said tube, an oscillation generator having anenergizing circuit coupled with the anode circuit of said rst namedtube, radiating means, a variable coupling between said radiating meansand the' output circuit of said oscillation generator, and means formoving selected pairs of the points on said potentiometers in oppositedirections.

9. A transmitter comprising a plurality of sources of alternatingcurrent of tone frequency, said frequencies increasing progressivelyfrom the rst source to the last source, a thermionic tube having ananode, a cathode and a control grid, a variable coupling device betweenthe output of each of said sources and the control grid and cathode ofsaid tube, means for varying the degree of effectiveness of each of saidcoupling devices and for producing such variations simultanepusly inopposite senses with respect to any two of said devices, an oscillationgenerator having an anode energizing circuit in common with the anodecircuit of said first named tube, radiating means, and a Variablecoupling Vbetween Y

